(1) Field of the Invention
This invention relates to metal oxide nanometric particles and to a process for the preparation thereof. In particular, the present invention uses a preformed carbon based template for forming the nano particles or a precursor to the nano particles.
(2) Description of the Related Art
Zeolites have been used extensively to catalyze a number of chemical reactions in refinery and petrochemical reactions, and mesostructured silicas have received much attention in diverse areas such as catalysis, adsorption, separation, and chromatography (Baerlocher, C. H., Atlas of Zeolite Framework Types, 5th ed.; Elsevier Science: Amsterdam, (2001)). Nanosized zeolites have been observed to have more catalytic activities than conventional zeolites with large particle size in refinery and petrochemical reactions, because fine particles in a nanometer scale have a remarkable potential as an easy-to-handle form having highly accessible mesopores from inter-particles (Yamamura, M., et al.,Zeolites 14, 643-649 (1994); Vogel, B., et al., Catalysis letters, 79, 107-112 (2002); Landau, M. V., et al., Industrial & Engineering Chemistry Research 42, 2773-2782 (2003); and Zhang, P. Q., et al., Catalysis Letters 92 63-68 (2004)).
Conventional methods for preparing metal oxides in nanometric particle form include the formation of the desired solid phase from reagents in a solution or gas phase. The solution phase approach generally requires very low reagent concentrations, the processing of large liquid volumes and, oftentimes, the presence of a particle growth regulator. Gas phase reactions are limited to the use of reagents that are volatile and to the formation of product phases that are stable at the temperatures needed to place the reagents in the gas phase.
In particular, zeolite nanoparticles have been prepared through careful control of the reaction stoichiometry, the crystallization time and temperature (Yamamura, M., et al., Zeolites 14, 643-649 (1994); Lovallo, M. C., et al., Advanced Catalysis and Nanostructured Materials, Academic Press: San Diego, (1997); Zhang, G. Y., et al., Chemistry of Materials 9 210-217 (1997); Hosokawa, H., et al., Chemistry Letters 32 586-587 (2003); and Hincapie, B. O., et al., Microporous and Mesoporous Materials 67 19-26 (2004)). On the basis of a modified Stober reaction process and the dilution quenching process, mesostructured silicas with the average particle size less than 100 nm have been prepared in highly dilute system (Cai, Q., et al., Chemistry of Materials 13 258-263 (2001); Nooney, R. I., et al., Chemistry of Materials 14 4721-4728 (2002); Sadasivan, S., et a l., Angewandte Chemie-International Edition 41 2151-2153 (2002); and Suzuki, K., et al., Journal of the American Chemical Society 126 462-463 (2004)).
U.S. patent application Ser. No. WO03/006372 A1 to Jaroniec et al., which is incorporated herein by reference, describes the formation of imprinted carbon structures. The carbon mesoporous structures have a diameter between about 1 nm to 30as a result of using the imprinting material. The imprinting material is colloidal silica. Pitch is a preferred carbon forming precursor. The imprinting material can be removed from the carbon structure by bases or acid, such as NaOH or HF. These carbon structures can be useful in the present invention.
U.S. patent application Ser. No. WO03/006372 A1 to Jaroniec et al., which is incorporated herein by reference, describes the formation of imprinted carbon structures. The carbon mesoporous structures have a diameter between about 1 nm to 30 as a result of using the imprinting material. The imprinting material is colloidal silica. Pitch is a preferred carbon forming precursor. The imprinting material can be removed from the carbon structure by bases or acid, such as NaOH or HF. These carbon structures can be useful in the present invention.